Fix Expression::Method#match_length

lib/mutant/expression/methods.rb

@@ -25,6 +25,22 @@ module Mutant
         MATCHERS.fetch(scope_symbol).new(env, scope)
       end
 
+      # Return length of match
+      #
+      # @param [Expression] expression
+      #
+      # @return [Fixnum]
+      #
+      # @api private
+      #
+      def match_length(expression)
+        if expression.syntax.start_with?(syntax)
+          syntax.length
+        else
+          0
+        end
+      end
+
     private
 
       # Return scope name

spec/unit/mutant/expression/methods_spec.rb

@@ -16,7 +16,13 @@ RSpec.describe Mutant::Expression::Methods do
       it { should be(object.syntax.length) }
     end
 
-    context 'when other is an unequivalent expression' do
+    context 'when other is matched' do
+      let(:other) { described_class.parse('TestApp::Literal#foo') }
+
+      it { should be(object.syntax.length) }
+    end
+
+    context 'when other is an not matched expression' do
       let(:other) { described_class.parse('Foo*') }
 
       it { should be(0) }